GM and other Dex VI licensees compatibility listing is conflicting/contradictory/incomplete.
GM says Dex VI is backward-compatible with SOME previous versions of Dexron, in SOME applications. It's NOT backwards-compatible with the early Hydromatic/Dynaslow that used engine oil, or transmissions that were specified for Type A, or Type A Suffix A; and early versions of Dexron. But again, info is contradictory/incomplete/subject to interpretation.
Non-GM vehicles that used Dexron may/may not be suitable for Dex VI.
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Mobil™ DEXRON-VI ATF is a high-performance, synthetic blend automatic transmission fluid formulation designed to meet the stringent service fill requirements of GM’s DEXRON-VI specification.
www.mobil.com
The Mobil web-page says
(My emphasis) Mobil is claiming total backwards-compatibility with all Dexron formulas. That covers back to Model Year 1967. Prior to that, it was some version of Type A, and before that...motor oil.
Another source saying Dex VI is only compatible with other Dexron applications.
By Walt Silveira, director of automotive products, lubricants, ConocoPhillips Company, Kendall, Phillips 66, 76 and Conoco brands. Related Articles - How To Properly Clean An Engine - The Hidden Expense of Inexpensive Brake Pads - AAPEX Web Training Series Set to Begin This Month The new...
www.counterman.com
I would be
willing to put Dex VI into any Dexron application. I don't because I still have a heap of Dex-Merc (Dexron III-compatible) fluid; and nothing I own is new enough to require Dex VI.